Post from sketch show entertaining great man in audience (5,4)
I believe the answer is:
snail mail
'post' is the definition.
(I've seen this before)
'great man in audience' is the wordplay.
'great' becomes 'snail' (I can't explain this - if you can you should give a lot more credence to this answer).
'man' becomes 'male'.
'in audience' indicates a 'sounds like' (homophone) clue.
'male' is a homophone of 'mail'.
'snail'+'mail'='SNAIL MAIL'
'from sketch show entertaining' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for snail mail that I've seen before include "old-fashioned correspondence?" , "Conventional (slow) post (informal)" , "Ordinary post" , "The conventional postal service" , "Modern jargon for letter post, mollusc-slow compared to electronic transport" .)